Water supersaturation modeling for Early Mars Climate during Noachian

Abstract

<p>Through today's observation of dry lakes, rives and large valley networks, we can assume liquid water abundantly flowed on Mars during the Noachian era, approximatively 4Gya. However, the climate that host this active water cycle is yet poorly understood. Recent modeling studies tried to reproduce the conditions that may have occured on the planet, trying to find an atmospheric process or composition that could solve the well known Faint Young Sun Paradox. Theses modeling studies, through the use of 3-dimensional Global Climate Models struggled to warm sufficiently the past climate of Mars, even considering different greenhouse gases, the role of clouds, meteoritic impact or even volcanism. However, the presence of H<sub>2</sub> could be an interesting solution for a sustainable warming as some recent studies suggest (Turbet and Forget, 2021). Another recent study (Ito et al. 2020) suggested that H<sub>2</sub>O<sub>2</sub> might be a convincing candidate but has to be in high supersaturation ratio in the atmosphere, even though it only used a simplified 1D model and relatively high supersaturation levels.</p><p>We try here to explore the scenario of supersaturated water, that might be a specy able to provide a sufficient global warming under supersaturated conditions or through the formation of high altitude clouds.  Through 1D and 3D modeling, we try to constrain the theoritical supersaturation level of H<sub>2</sub>O that will allow the warming of the climate above 273K. Our results suggest that in an atmosphere only composed of CO<sub>2</sub> and H<sub>2</sub>O, water supersaturation can create a significant warming but only with with supersaturation levels in the lower layers of the atmosphere, although it can be seen as unrealistic. We describe in this work the effect of supersaturation on temperatures, clouds, and the water cycle of the simulated planet. Even if we do not tackle the question whether the supersaturation hypothesis is realistic or not, these results give a better understanding of what would be Early Mars' climate under such conditions.</p>